1. Field of the Invention
The present invention relates to the filed of reciprocating electromagnetic devices, and in particular to a solenoid driven pump having a magnet attached to the reciprocating piston activating a hall effect switch to produce a signal having a magnitude and polarity indicative of the position of a reciprocating piston.
2. Description of the Prior Art
Reciprocating piston electromagnetic fluid pumps as disclosed in the patents to Parker U.S. Pat. No., 2,994,792, and Wertheimer, U.S. Pat. No. 3,381,616, have obtained wide commercial acceptance, but in a highly competitive field, improvements are very important. The earlier models of these pumps, as represented by Parker, include an electrical switch in circuit relationship with a solenoid which is either mechanically or magnetically actuated by the piston at the end of the pumping stroke. Closing the switch energizes the solenoid retracting the piston to its cocked position. When the piston reaches the cocked position, the switch opens, deenergizing the solenoid and the pumping stroke is carried out under the force of a compressed spring. Although these types of pumps function very satisfactorily and have a reasonable operating life, the electrical switch is subject to failure and is determinative of the pump's operating life.
To increase the life of the pump, blocking oscillators were subsequently introduced such as taught by Wertheimer and Brown in U.S. Pat. No. 3,629,674. Blocking oscillators eliminated the electrical switch and increased the operating life of the pump.
Disclosed herein is a reciprocating piston electromagnetic fluid pump in which the mechanical switch is replaced by a hall effect switch generating a signal having a magnitude and polarity indicative of the piston's position.